As the temperature drops below 10 deg C, the bees are clustering in the centre of the hive. You can see them below in between the central 6 frames. The 4 frames either side are empty of bees for now but still carry stores sot eh cluster will move across the frames as the stores are consumed. If you could look at a cross-section of this cluster from the side, it would look like a rugby ball. The Queen is in the centre of the cluster which is maintained at 35 deg C. They do this by vibrating their wing muscles to generate kinetic heat. That's why they need carbohydrate energy throughout the Winter - they never actually hibernate, they just stop moving around and keep warm.
Every now and again, I will tip the hive to get a feel for its weight. If it feels light, I will put some fondant on top because that means they have consumed most of the stores. There's not much more to say at this time of year. If we get a sunny and relatively warm day, the bees will fly just outside the hive on a 'cleansing' flight. You see, they are very hygienic and will not 'poop' inside the hive - they hold it in for a warmish day then rush out for a brief flight to the ablutions.
You can see from the reflections that I use a perspex crown board instead of a solid wooden one so I can see if they are ok without taking the lid off and letting all that heat escape.
Photo: Bakers fondant on top of an access hole for hungry bees in Winter. I cut a hole in the fondant tray, turn it upside down and natch it to the crown board hole, immediately above the cluster of bees. I can't use the perspex crown board for this as it does not have a hole in it.